Merge pull request #21 from gusferguson/version_5-1-0_release-1

Remove Editor page from Help site - delete menu entry, html file, images
Adding a custom error page

The page redirects you to:
http://help.openmicroscopy.org/
Making redirect instant
Merge pull request #23 from qidane/error-page-redirect

Adding a custom error page
Change Resources page to Training Course Material page